This invention relates generally to power generation and distribution systems and, more particularly, to a method and apparatus for selectively changing a generator set output rating.
Engine generator sets (hereafter referred to as xe2x80x9cgensetsxe2x80x9d or in the singular as xe2x80x9cgensetxe2x80x9d) of a wide variety of sizes and power load capacities are commonly utilized as prime or backup power sources for a wide variety of electrically driven equipment in applications and locales having different requirements. For example, many locales require gensets to meet specific exhaust and noise emission levels. One locale may require low levels of particulates and Nitrous Oxides (NOX) compared to other locales. Another site may require even lower particulates but allow greater levels of NOX. Still another may have no exhaust emission requirements. Similarly, regulations on noise emissions also vary from location to location.
In addition to different emission requirements, genset applications may have different power requirements. One site, for example a remote quarry, may use the genset as its primary power source and need continuous power. Another site, for example a hospital, may use the genset for standby power. A genset used as a standby or auxiliary power source is generally able to run at a higher power rating than the same genset used as a prime power source.
Voltage and frequency requirements of equipment powered by the genset vary as well. For instance, in the United States 480V and 60 Hz is a common requirement for electrical equipment, whereas European applications are more likely to need 400V and 50 Hz power. Gensets that are able to provide a certain power level at one voltage and frequency may not be able to supply the same power at another voltage and frequency.
By changing the software instructions controlling genset operation, an electronically controlled genset can produce different ratings optimized for different application requirements with no mechanical changes. For example, a genset may be controlled by software instructions that produce a rating with characteristics of 60 Hz, certain emission regulations, the best possible fuel economy for that point of operation and 480V. The same software instructions may not produce a rating that meets emission requirements and genset physical limitations if the engine were running at 50 Hz and 400V. But, another set of software instructions can be developed to produce a rating that meets emission requirements and genset physical limitations at 50 Hz and 400V.
Typically, a service tool is needed to change the rating of an engine. A variety of service tools are available for this task, such as a computer device or personal digital assistant capable of physically connecting to the ECM. Sometimes the engine rating software instructions must be loaded or flashed into the ECM; other times the ECM contains a plurality of sets of software instructions, each producing a specific engine rating, and the service tool is used to select one.
Typically, a voltage regulator is adjusted manually or with a service tool to control the genset voltage. Voltage regulators are typically designed to operate with a variety of different gensets with a wide range of capabilities. Thus, a particular genset, may not be capable of operating at all voltage choices available on a voltage regulator. For instance, a choice on the voltage regulator may be 600V, but the generator may be physically unable to operate at 600V, going into saturation at 550V. A technician has to know the limitations of the genset when setting the voltage and frequency on the voltage regulator.
In addition, the genset may not be able to meet the same power rating at one voltage as it can at another voltage. For instance, a genset may be able to produce 400 ekW at 240V, but only 380 ekW at 208V. If a technician changes the voltage for a genset, he or she must know when also to change the current engine rating to a different engine rating with a lower maximum power.
In addition to setting the engine and voltage ratings for a particular application, a technician may also need to set relays and other protective devices contained in the genset control system. Protective relaying, such as over and under voltage relays and over and under frequency relays, disconnects a load, shuts down the engine, prevents excitation of the generator or protects the genset in some other manner if a condition that could cause damage to the genset is detected. For example, if the voltage exceeds the acceptable rating and the genset has an overvoltage relay, the relay may trip a circuit breaker and disconnect the load, thus preventing damage to both the generator and the load. Relays must be set correctly to operate. For example, the voltage level at which the overvoltage relay will trip a circuit breaker is typically set manually or with a service tool. A technician must know the correct value at which to set this voltage.
To change the rating of a genset, a technician may need a variety of skills. He or she may need to use a service tool to change the engine rating; he or she may need to change the voltage and frequency on the voltage regulator manually or with a different service tool. The technician may further need to set protective relays and ensure all settings are compatible with each other and the genset. It may be difficult, especially in remote areas where gensets often run, to find technicians with these skills. In addition, the more steps the technician has to take to setup a genset, the more chances there are for error. It would be preferable to have a control system that overcomes these and other disadvantages.
In one aspect of the present invention, an apparatus for changing a genset rating is disclosed. The apparatus includes a control system for controlling a genset, the control system having at least two genset ratings stored therein and a rating selector, each of the genset ratings including at least an engine rating and a voltage, the rating selector having an operator input.
In another aspect of the present invention, a method for changing a genset rating is disclosed. The method includes the steps of selecting one of a plurality of genset ratings wherein the genset ratings are stored in a control system for controlling the genset and the genset ratings include at least one associated engine rating and a voltage, setting the associated engine rating, and setting the associated voltage.
In still another aspect of the present invention, a method for changing a genset rating is disclosed. The method includes the steps of selecting one of a plurality of genset ratings wherein the genset ratings are stored in a control system for controlling the genset and the genset ratings include at least one associated engine rating and a voltage, determining if the genset is running or attached to a load, setting the associated engine rating if the genset is not running or is not attached to a load, and setting the associated voltage if the genset is not running and not attached to a load.